Process of making zinc-coated ferrous wire



i938. F, M. cRAPo PROCESS OF MAKING ZINC COATED FERROUS WIRE Filed oct. 25, 1955 N @NG QMS .MNC

May 24,

NEW@

50. tusdiagrammatically. In that drawing, Fig. l is quenching is to be done; so that the tempera- 50 and in additionfan apparatus for a preliminary raised by the baths I2 and I4, and by the fur- 55 Patented May 24, i938 PROCESS F,MAKING ZINC-COATED FERROUS WIRE Frederick M. Crapo, Muncie, Ind., `assignor to Y Indiana Steel & Wire Company, Muncie, Ind.,

a corporation of Indiana Application October 25, 1935, Serial No. 46,782

y .En Canada June 5, 1934 io claims. (c1. sii-70.3)

It is the object of my invention to produce salt treatment andan apparatus for asubsequent zinc-coated ferrous wire which is of relatively zinc-coating treatment; and Fig. 2 is a diagram low carbon content but which has both high showing the contents of carbon and manganese tensile strength and good zinc adhesion. in the carbon-steel wire, the area in solid-line Ferrous wires with good zinc adhesion, even cross-hatching indicating the preferred area, 5 with very low carbon content, have been made. and the area in broken-line cross-hatching indi- Among such wires are those shown in the Crapo eating the permissive area.

Patent No. 1,501,887, granted July 15, 1924; in The apparatus shown diagrammatically in Fig.

. the Crapo Patent No. 1,552,041, granted Septem- 1 is for carrying out my invention on ferrous ber 1. 1925; and in the Crapo and Baylis Patent wire l0 of the character shown in Fig. 2. 'I'hat is, 10 No. 1,545,305, granted July 7, 1925. it is a carbon-steel wire in which the carbon is My co-pending application Serial No. 705,831, below 0.50%, and desirably below 0.25%; and led January 8, 1934, now Patent No. 2,019,445, the manganeseis also fairly low, in anycase be- ,J granted October 29, 1935, is directed to an eleclow 1.0% and desirably below 0.50%, and below 10 tric transmission line embodying a ferrous wire 0.30% when the carbon exceeds 0.25%. Silicon, 10

of relatively low carbon content but of high phosphorus, and sulphur may be present in the tensile strength. My present application is diamounts common in carbon steels. These carrected to the process of making and zinc-coating bon steels may be copper-bearing steels. such a Wire, and more especially the wire made This carbon-steel wire I0, which may already use of in that application. have been subjected to some or all of any desired l20 While other wires with both good zinc adhewire-drawing before reaching the` apparatus sion and high tensile strength are known, in shown in Fig. 1, is ordinarily passed rst through general they have been rather high in carbon; a pickling or other cleaning bath II. Then it is whereas my present invention is directed to the passed through a'heating device, which is prefcombining of good zinc adhesion and high tenerably in the form of a molten-lead bath I2; 25 sil'e strength in a ferrous wire of relativly low from which it emerges through a band or rim I3 carbon contentin any event less than 0.50% carof 'the type shown in the Crapo and Baylis Patent bon, and desirably less than 0.25% carbon-and No. 1,545,305 already referred to. Within the with the manganese desirably below 0.50%, and lband or rim I3 is a bath of molten salt I4, which 0 below 0.30% when the carbon exceeds 0.25%. is of such character, as by containing .cyanide or 30 In carrying out my invention, I treat such a cyanamid, that it produces by chemical change ferrous wire at elevated temperature, preferably such a permeative addition on the surface of in a molten-salt bath of suitable character, to the -wire I 0 that adhesion of a subsequently produce on the surface of the wire by chemical applied zinc coating is improved, as set forth change a permeative addition of material of the in my prior Patent No. 1,501,887 already re- 130 class consisting of carbon and nitrogen and phosferred to. As the wire I0 passes through the phorus, and thereafter quench the wire from a molten material of the lead bath I2, and/or of temperature at least as high as the Aci critical the salt bath I0, it is heated toward or to the temperature, and desirably from a temperature desired temperature from which it is later to be 40 at least as high as the Acc critical temperature, in quenched;` so that less additional heating or even '11 a liquid medium which has a temperature below no additional heating is required before subsethe melting point `of lead; and then I coat the quent quenching. That is, the heating within wire with zinc, desirably by a hot-galvanizing the baths I2 and I4 may in some cases be suiliprocess in which I also'partially draw the temper cient to raise the temperature of the wire I0 to of the wire by heat treatment after the quenchthe desired value from which it is to be quenched. f ing. Ordinarily, however,.the wire I0 on leaving the Various types of apparatus may be used for molten-salt bath I4 passes into a heating furcarrying out the process of my invention. In the nace I5, in which-its temperature is further eleaccompanying drawing I show one such apparavated to the desired temperature from which 'a diagram-matic view of a heating and quenching tures of the molten lead and of the molten salt apparatus,` with a subsequent tempering appamay be lower than when these baths are reratus and a subsequent wire-drawing apparatus, quired to do all the heating prior to quenching. either or both of which may be used if desired, The temperature to Which the Wire is thus canv nace I5 if it is used, is at least as high as the Aci or lowermost critical temperature, and desirably as high as the Ac: or uppermost critical temperature. As is well known, these critical temperatures vary with the composition of the ferrous material.

The heating furnace I5 is conveniently but not necessarily of the mule type. The atmosphere within it may be of any suitable character. Such atmosphere may be one which in itself tends to produce by chemical change in the surface of the ferrous wire a permeative addition which tends to promote the adhesion of a subsequently applied zinc coating, such as ammonia gas (of the Crapo Patent No. 1,552,041 already referred to) or phosphine gas; in which case the bath I4 of molten cyanide or cyanamid may be omitted.

From the heating furnace I5, the wire I0 passes immediately into a quenching bath I 6, in which while still at or above the critical temperature it is immediately immersed in a liquid quenching medium. Such quenching medium is one which in any case has a temperature below the melting point of lead, and in many instances desirably has a temperature at or below the boiling point of water; This quenching from at or above the critical temperature to this relatively low temperature carries the temperature of the carbon-steel wire very rapidly downward through the critical temperature range, so that the wire then has high tensile strength.

The liquid quenching medium may be water,`

or any desired aqueous solution, especially for ferrous wires in the lower range of carbon contents, say below 0.25%. Oil, or other suitable organic liquid, may also be used for the quenching medium. So may a low-melting salt or mixture of salts, or low-melting metal or alloy, melting in any case below the melting point of lead.

After the wire I0 leaves the quenching bath I6, a partial drawing of its temper is often desirable, especially in wire of the higher carbon contents (within the range of my invention), when the quenching has been in a quenching medium of the water type, and/or when the subsequent zinc-coating is by a cold process. This may be obtained by passing the Wire through a suitable tempering furnace I 1. When such a` tempering furnace is employed, it raises the temperature of the wire to the temperature necessary for drawing the temper to the desired extent.

The temperature of the tempering furnace I1 may vary with the composition of the wire, usually being higher as the carbon content is greater; with the suddenness and extent of the chilling produced by the quenching, usually being higher as such chilling has been more drastic; with the character of subsequent treatments, such as whether the subsequent zinc-coating is by the hot-dip process or by a cold process such as electro-plating; and with the tensile strength and other characteristics desired in the wire.

After leaving the quenching bath I6 (and the tempering furnace I'I if it is used), the wire I0 is suitably zinc-coated. Preparatory to this it is usually passed through any of the well-known preliminary treatments, such as a pickling bath I8 and a fiuxing bath I9. After these preliminary treatments, the wire I 0 passes to the zinc-coating bath 20.

The zinc-coating bath 2,0 may be of any desired character, to deposit zinc either hot or cold-as by hot-dipping or by electro-deposition. Desirably it is a hot-galvanizing tank, in which case the zinc is maintained molten by suitable heating means 2I shown diagrammatically below the zinc-coating bath 20. By having the zine-coating bath a hot-galvanizing bath, it is of especial advantage to use the bath of molten salts I4, to promote adhesion of the zinc to the ferrous wire. Moreover, when the coating bath 20 is a hot-galvanizing bath it inherently involves a heat treatment of the wire I0 passing through it. That heat treatment partially draws the temper of the wire from the greater hardness produced in the quenching bath I6, so that it is then commonly not necessary or desirable to use a tempering furnace I1 in addition; but my invention does not preclude the use of both on the same wire, for the extent of the tempering may be varied as desired in my invention.

From the zinc-coating bath 20, the wire I0 passes to a take-up reel 22, by which power is applied to the wire for pulling it through the apparatus.

If desired, one or more Wire-drawing dies 23 may be provided to act on the wire after it has been quenched and/or after it has been zinccoated. The drawing produced by these dies supplement-s the increase in tensile strength obtained by the quenching.

By the process which has been described, a zinc-coated ferrous wire of relatively low carbon content may be obtained which has both a tensile strength which is high and a zinc adhesion which is superior, as compared with ordinary ferrous wires of corresponding carbon content.

'I'he apparatus shown in the drawingfis merely illustrative, and may be varied in many respects. My invention does not depend on any particular apparatus. Instead, it is directed broadly to the process as defined in the appended claims.

I claim as my invention:

1. The process of treating a steel wire which contains less than 0.50% carbon, and which contains less than 0.30% manganese when the carbon exceeds 0.25%, which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as high as the Aci critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

2. The process of treating a steel wire which contains less than 0.50% carbon, and which contains less than 0.30% manganese when the carbon exceeds 0.25%, which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as high as the Aca critical temperature in a liquid medium having a ternperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

3. The process of treating a steel wire which contains less than`0.50% carbon, and which contains less than 0.30% manganese when the carbon exceeds 0.25%, which consists in passing said wire through a molten-salt bath which by chemical change produces on the surface of the wire a permeative addition of material of the class consisting of carbon and nitrogen, thereafter quenching the wire from a temperature at least as high as the Aci critical temperature in a liquid medium amarte having a temperature below the melting point o lead, and then zinc-coating it by the hot-dip process.

4. The process of treating a steel wire which contains less than 0.50% carbon, and which contains less than 0.30% manganese when the carbon exceeds 0.25%, which consists in passing A said wire through a molten-salt bath which by chemical change produces on the surface of the Wire a permeative addition of material of the class consisting of carbon and nitrogen, thereafter quenching the wire from a temperature at least as high as the Aca critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

5. The process of treating a steel wire which contains less than 0.25% carbon, which consists in subjecting said wire to an'elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as high as the Aci critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

6. The process of treating a steel wire which contains less than 0.25% carbon, which consists in subjecting said wire to an elevated temperature under conditions.which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as high as the Aca critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

'1. The process of treating a steel wire which contains less than 0.25% carbon and less than 0.50% manganese. which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as high as the Aci critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

8. The process of treating a steel wire which.

contains less than 0.25% carbon and less than 0.50% manganese, which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenchingthe wire from a temperature at least` as high as the Ac: critical temperature in a liquid medium having a temperature below the melting point of lead, and then zinc-coating it by the hot-dip process.

9. The processof treating a steel wire which contains between 0.25% and 0.50% carbon and not in excess of 0.30% manganese, which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting-of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at leastas high as the Aci critical temperature in a liquid medium having a temperature below the melting pointof lead, and then zinc-coating it by the hot-dip process.

10. The process of treating a steel wire'which contains between 0.25% and 0.50% carbon andv not in excess of 0.30% manganese, which consists in subjecting said wire to an elevated temperature under conditions which produce on its surface by chemical change a permeative addition of material of the class consisting of carbon and nitrogen and phosphorus, thereafter quenching the wire from a temperature at least as lhigh as the Aca critical temperature in a liquid me- Ldium having a temperature below the melting DERICK M. C 

